One of the most popular choices for printing is web offset. Ideal for very high print runs, web offset is most commonly used of all the rotary printing types.
Before any further explanation is given, it’s important to note that the ‘web’ in web offset printing refers to the machine type. Web offset machines use large rolls of paper that run through the machine in a continual line. Web offset printing allows both sides of the paper to be printed simultaneously.
The colour used in web offset is transferred from the printing plate using an additional rubber blanket cylinder roller to the paper.
Coldset and Heatset
In web offset printing, there are two distinct drying processes following printing. These are coldset and heatset.
Coldset is used where the printing of newspapers is being done. In this process, drying occurs slowly as ink dries on its own. You can tell an item that’s been dried using the coldset process, as the ink will sometimes transfer to your fingers, such as can happen with newspapers. Coldset printing is usually done vertically on paper rolls, and can take as many as 5 working days to completely dry. Therefore, turnaround time for web offset printing using the coldset drying process can be lengthier.
In heatset, just-printed paper passes through an oven, drying the ink immediately at 250 °C, before cooling it immediately to a maximum of 30°C. Because of this, images take on an attractive sheen. The heatset drying process is most often used when magazines, brochures and catalogues are being printed, and is done horizontally.
Most customers choose web offset because of the high speeds that large volumes of products are able to be printed. But how fast is it? Usually, a web offset printer can achieve speeds of 65,000 revolutions per hour. This can result in millions of prints being able to be produced in a small amount of time.
Whether chosen for the printing of inkjet labels or documents, web offset printing definitely offers a higher quality end product. Image quality is especially enhanced when web offset printing is used. However, this is partly due to the fact that the technology which transfers images from computer to place is more developed today. Not only that, but there are consistently high-quality results with this type of printing.
The cost of web offset printing tends to be more upfront. This is because setup must be done. In web offset printing, each plate represents a single colour: cyan, yellow, magenta or black. As well, plates must be made.
Materials, Ink and Varnish
Web offset printing offers a large choice of materials that go beyond paper to rubber, fabric and wood. In addition, choosing a specialist stock of paper can mean a lower cost with larger web offset runs. For inks, those looking to have their inkjet labels or other products printed with the web offset process can use speciality varieties such as metallic ink without worry. The same is true of those looking to have a UV varnish applied to their printed products, as web offset printing can handle this quite well.
At the end of the day, the choice to use web offset printing will depend solely on the nature of your product as well as your deadline. Whilst the machine setup for web offset printing may be somewhat complex, the printing of multiple copies can be completed quite efficiently.
Digital printing, web offset`s counterpart can complement the latter, and as such should not compete with web offset printing. Rather, the strengths of both types can be used to benefit a printing project.